Process for the production of metallic magnesium and fixed nitrogen



June 7 1927. -1 c. G. MINER PROCESS FOR THE PRODUCTION OF METALLIC MAGNESIUM AND FIXED NITROGEN Filed NOV. 6, 1922 w m nu Patented June 7, 19271.l

UNITED STATESv PATENT OFFICE.

CLAUDE G. MINER, 0F BERKELEY. CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS,

T0 ANGLO-CALIFORNIA TRUST COMPANY, TRUSTEE, 0F SAN FRANCISCO, CALI- EoRNIA.

PROCESS FOR THE PRODUCTION 0F METALLIC MAGNESIUM AND FIXED NITROGEN.

Application filed November 6, 1922. -Sicrial No. 599,289.

This invention relates to a process for the production of metallic n'iagnesium and for the fixation of nitrogen, said process involving generally first the treatment of nxagnesium-bearing ores for the production of intermediate magnesium nitrogen compounds, and second the treatment of the magnesium nitrogen compound or the material containing it with a metathesis agent, whereby metallic' magnesium is liberated and a nitrogen compound of the metathesis agent is formed.

At the present time it is common praetice to produce met-allie magnesium by electrolytic action upon fused magnesium chloride using alkali metal chlorides as electrolytcs or by electrolytic action upon magnesium oxide using certain fluorides as electrolytes. But magnesium chloride and magnesium oxide have relatively high heats of formation and do not lend themselves to a cheap and practical process for the production of metallic magnesium. An object of the present invention ,therefore is the preparation of metallic magnesium from compounds thereof having a lower heat of formation than the chloride and oxide. I have found that by treating magnesiumnitrogen compounds with metathesis agents at comparatively low temperatures metallic magnesium is liberated in vapor form and nitrogen compounds of'the metathesis agent having a considerable commercial value are produced.

The magnesium nitrogen compounds such as magnesium nitrid and carbonitrid (designated cyanamid by some authorities) may be treated withv a, variety of metathesis agents under a variety of different temperature and' atmospheric conditions. For eX- ample. magnesium-bearing ores, such as magnesite, dolomite, brucite, and the like, mayv he reduced and treated to-form magnesium nitrid or carbonitrid, after which the product. may be brought into intimate contact with a metathesis agent such as aluminum, boron, chromium, molybdenum, silicon, titanium, tungsten. uranium, vanadium, calcium, barium o1' combinations thereof or ferro alloys thereof. Any ofthese agents will act to liberate metallic magnesium from the nitrid or carbonitrid at a temperature in excess of 11200- C.. this being Y the vaporization temperature of magnesium,

Referring to the drawing, 11 indicatesa rotary furnace `into which magnesite or other magnesium-bearing ore previously reduced to a finely divided state is fed'from the feed hopper 10. When the ore has been partially or completely dehydrated and alcined it is delivered or allowed to pass into the rotary furnace 12. Furnaces-11 and 12 are set at a slight inclination so that the ore -will pass slowly therethrough by gravity. Thelower end of the furnace 12 is heated to between 1000 C. and 1700 C., for instance by electrical heating means incorporated in the construction of the furnace. In the furnace 11 the ore ,is heated to a tei'npaerature of about 1500"' C. Interposed between the furnaces 11 and 12 are carbonaceous feed device 13 and an air feed pipe 14. Carbonaceous material, preferably pulverized coke or coal, is fed through the device-13 in such quantities as to bring about the reduction of the magnesium oxide content of the ore Within the furnace. Air is supplied through the feed pipe 14 to sustain` promote, increase and regulate the combustion of residual material in the calcining furnace and the gases passing from the .furnace 12 in which nitrogen lfixation takes place. In case magnesium nitrid is desired, the temperature of the furnace 12 is maintained at 1500 to 1700 C., nitrogen or producer gas rich in nitrogen4 being supplied at the lower end of the furnace 12 through the pipe 30. At a temperature of 1500 to 1700o C. magnesium oxide mixed with carbon in an' atmosphere of nitrogen or. producer gas rich in nitrogen isv converted to magnesium nitrid in accordance with the following reaction equation:

3 Mgo-taoJFNFMgNa Veo The furnace product containing magnesium nitrid drops through the chute 17 and is Ithe longest possible time.

forced by the ram 19 into the electrically heated retort 20--21, where it is treated wit the metatliesis agent, the metallic magnesium vapors so forinedpassing through the conduit 22 and collecting in the condenser 23.' A 75 to 90% ferro-silicon alloy is the preferred metathesis agent. It may be prepared on the spot in the furnace 29 and delivered directly in molten forni intov the retort 20 through the pipe 31. Ferro-silicon is not only inexpensive but the iron content thereof assists the reaction. IVhen using ferro-silicon and a. reaction temperature at or slightly above the melting point thereof the reaction mixture remains in molten condition, thus facilitating the removal from the retort of the silicon nitrid formed, and moreover the formation of a' skin of silicon nitrid lupon the magnesium nitrid as when silicon is used as the metathesis agent, is prevented and the completion of the reaction thus facilitated. The magnesium vapors generated in the retort 20 are collected in the condenser 23 `from which magnesium may he i'un off in pig form. The reaction residue containing silicon nitrid is discharged from the retort through the conduit 24 into a receptacle 25. Silicon nitride is an excellent fertilizer, claimed by some authorities to be superior to calcium cynamid.

The foregoing procedure. is continuous and eliminates the ditliculties heretofore encountered in the manufacture of magnesium.

Instead of forming magnesium nitrid as described above the magnesium content of the ore may first be converted to magnesium carbonitrid from which magnesium is liberated by the action of a suitable metathesis agent with the formation of the carbonitrid thereof. For this purpose the procedure may be as follows:

The magnesium-bearing ore is calcined inthe rotary furnace 11v up to a temperature of 1200-1500o C. and then passes into the furnace 12 whichv is maintained at. a temperature of 1000 to 1500o C. Nitrogen and hydrocarbons capable of reacting therewith in the presence of a high tension arc to form hydrocyanic acid such as acetylene, natural gas, methane. crude oil vapors, etc., or nitrogen, hydrogen and carbonaceous material are injected into the lower end of the furnace 12 and a high tension are is arranged and maintained in the lower part of the furnace in such a way that the material injected will be in contact with it for In this case it is not necessary' to feed carbonaccous material at 13 as in the method of making niagnesium nitrid described above. Under the conditions stated the magnesium oxide content of the ore and the nitrogen and hydrocarbon or nitrogen, hydrogen and carbonaceous material react forming magnesium earbonitrid. Theoretically the nitrogen and hydrocarbon or nitrogen, hydrogen and carbon combine in the resence of tlic'liigh tension arc forming flCN'ivhich then reacts with tlic magnesium oxid, forming the cai-- lionitrid according to the followingreaction equation:

The furnace product containing the inagnesiuni carbonitrid then passes to the retort 202l Where it is treated With a metathesis agent for the liberation of metallic magnesium vapor and the formation of the carbonitrid of the metathesis agent. A variety of metathess agents may be employed, but in this case an aluminum-ferro-silicon alloy containing 60% to 90% of aluminum is preferred. Such an alloy may be prepared on the spot in the furnace 29 by the direct reduction of bauxite or other aluminous material` iii accordance with the method Worked out by Minot ofFrance, and delivered directly into the retort. The reaction between the magnesium cyanamid and the aluminum-ferro-silicon alloy is carried out preferably at a temperature of about 10000 C. under partial vacuum but may be carried out at atmospheric pressure using a temperature of say 1200 to 1500o C. The magnesium content of the magnesium carbonitrid is liberated, vaporied and recovered as described above, While the aluminum content of the alloy is converted to cyanamid and remains in the retort With the silicon and iron content of the alloy. The temperature at which the nietathesis is carried out should not exceed about 1500 C., as at The aluminum cyanamid formed in accordance with the foregoing procedure may be converted to aluminum chloride with the production of sodium cyanide by heating it with sodium chloride at a temperature of 800 to 900 C.

Instead of the aluininum-ferro-silicon alloy referred to in the foregoing example Other metathesis agents may be used for the conversion of the magnesium cyanamid, among which may. be mentioned ferro-titaniuin runningr about 75% titanium and ferrosilicon running from about 75% to about 90% of silicon. The reaction is best carried out at a temperature sufficiently high' to maintain the metathesis agent, in case ferro alloys are used, in molten form but in any case the reaction must be carried out at a temperature sufficiently high to vaporize the magnesium, i. e. 1120o C. at atmospheric pressure or at a lower temperature under reduced pressure.

It is naturally possible for one skilled in the art to vary the details of procedure described above as well as the proportionsof-ingredients, temperatures and other conditions without departing from my invention, the scope of which is indicated in the appended claims.

Claims:

1. Process of preparing metallic magnesium which comprises reacting upon a compound of magnesium having a heat of formation less than that of magnesium oxid with an'agent capable of liberating magnesium therefrom.

2. Process of preparing metallic magnesium which comprises reacting upon a compound of magnesium having a heat 'of formation less than that-of magnesium oxid with an agent capable of liberating magnesium therefrom at a temperature of at least 1120o C.

3. Process ofI preparing metallic magnesium which comprises reacting upon a compound of magnesium having a heat of formation less than that of magnesium oxid with an agent capable of liberating magnesium therefrom at an elevated temperature `under a pressure less than atmospheric pres- Sure.

4. Process of preparing metallic magnesium which comprises reacting upon a coinpound of magnesium having a heat of formation less than that of magnesium oxid With an agent capable of liberating magnesium therefrom and of uniting with the other elements thereof to form a compound having a vaporizing temperature above that of metallic magnesium.

5. Process of preparing metallic magnesium which comprises reacting upon a magnesium-nitrogen compound With an agent capable of liberating the magnesium content thereof.

6. Process of preparing metallic magnesium which comprises reacting upon a magnesium-nitrogen compound with an agent capable of liberating the magnesium content of said compound and of combining with the other elements thereof to form a compound having a higher volatilizing temperature than magnesium.

7. Process of preparing metallic magnesium which comprises reacting upon a magnesium carbonitrid with an agent capable of liberating the magnesium content thereof.

8. Process of preparing metallic magnesium which comprises reacting upon a magnesium carbonitrid With an agent capable of liberating the magnesium content thereof at @temperature and pressure capable of volatilizing the liberated magnesium.

9. Process of preparing metallic magnesium which comprises reacting upon a magnesium carbonitrid With an agent capable of uniting with the carbonitrid radical to form a compound having a higher volatilizing temperature than magnesium.

. nesium from said compound and of uniting with the other elements thereof to form a nitrogen compound of said agent having a volatilizing temperature above that of magnesium.

12. Process of preparing metallic magnesium from a magnesium-bearing ore,

which comprises converting the magnesium content of the ore to a compound having a heat of formation less than that of mag` nesium oxid and treating the ore with. an agent capable of liberating magnesium from said compound.

13. Process of preparing metallic magnesium from magnesium oxid, which comprises converting the magnesium oxid to a compound having a lower heat of formation than the oxid and treating the compound at an elevated temperature with an agent capable of liberating magnesium therefrom.

14. Processof preparing metallic magnesium which comprises calcining a magnesium-bearing ore to form magnesium oxid, treating said oxide with a carbonaceous material in the presence of nitrogen at an elevated temperature, and treating the resulting material with a metathesis agent capable of liberating magnesium from magnesium nitrid.

15. Process of preparing metallic magnesium which comprises calcining a -mag-. nesium-bearin ore to form magnesium oxid, subjecting sai magnesium oXid at an elevated temperature to an atmosphere of gases capable of forming hydrocyanic acid in the presence of a high tension are, and treating the resulting material with a metathesis agent capable of liberating magnesium from` magnesium-carbon-nitrogen compounds.

16. Process of preparing metallic mag nesium Which comprises calc-ining a magnesium-bearing ore to form magnesium oxi'd, subjecting said magnesium oXid at an elevated temperature to an atmosphere containing nitrogen and a hydrocarbon in the presence of a high tension arc, and treating the resulting material with a metathesis agent capable of liberating magnesium from magnesium-carbon-nitrogen compounds.

17.. Process of, preparing metaillc magnesium which comprises subjecting magnesium oxide at an elevated temperature to an atmosphere containing 'about 20 parts of methane` parts of hydrogen and 70 parts of nitrogen in the presence of a high tension are. and treating the resulting magnesiumcarbon-nitrogen compound with a metathesis agent capable of liberating the magnesium from said compound.

18. Process of preparing metallic inagnesiunl which comprises subjecting magnesium oxid ata temperature of 1000-15000 C. to an atmosphere containing a hydrocarbon and nitrogen in the presence of a high tension are. and treating the resulting magnesium-carbon-nitrogen compound with an aluminum-ferro-silicon alloy1 containing 60- 90 percent of aluminum at a temperature in excess of /1120 C.

19. Process of preparing metallic inagnesium which comprises subjecting magnesium oxid at a temperature of about 1000- 1500 C. to an atmosphere containin a hydrocarbon and nitrogen capable of orming hydrocyanic acid in the presence of'fa high tension are, and treating the resulting magnesium-carbon-nitrogen compound with a I0-90 percent ferro-silicon alloy at a temperature of about 1000-1600" C.

Process of preparing metallic magnesium which comprises preparing magnesiumfcarbonitrid from a magnesium-bearing ore` and treating the magnesium carbonitrid with a ferro-silicon alloy at a temperature in excess of 1120 C.

Signed at Berkeley in the county of Alameda and State of California this 7th day of March, 1922.

CLAUDE G. MIN ER. 

